------------------------
To turn root logins off, edit /etc/ssh/sshd_config and change
#PermitRootLogin yes
to
PermitRootLogin no
Save changes to make them permanent, and you won't have to worry about it anymore.
------------------------

Don't forget restarting sshd or atleast HUP'ing it ;)

From the sshd man page:
sshd rereads its configuration file when it receives a hangup signal, SIGHUP, by executing itself with the name it was started as, i.e., /usr/sbin/sshd

I know this is fairly obvious to most, but for those who are not aware, this may cause a BSD box (with its amazing stability) to be up for quite some time with an "insecure" sshd.